Irrigation Management for River-Salinity Control

The salinity of a given river system is the result of both salt-concentrating and salt-loading effects. Concentrating effects are produced by evaporation, diversion of high-quality water from the basin, and consumptive use by natural vegetation and by irrigated crops. The salt loading effects occur through dissolving action in the soil and the underlying materials. The water for this latter process originates from both irrigation applications and from precipitation that infiltrates into the soil matrix. Because a significant contribution to the total salt load of the upper Colorado River system originates from irrigation return flows, a procedure is needed that will predict the effects of irrigation management on salt inputs to the river. The paper presents the concepts and input data used in developing a one-dimensional streamflow and salt mass-balance model for long-run average effects of irrigation efficiency on salinity.